<!DOCTYPE html>

<html>

<body>
    <h3>Hello World</h3>
    <div id="myDiv">click me</div>
</body>

<script>
    var xhr = new XMLHttpRequest();
    xhr.open("post", "http://localhost:3000");
    xhr.setRequestHeader('Content-Type', 'application/json');
    xhr.send(JSON.stringify({
        username: "admin",
        password: "123456"
    }));
</script>

</html>